Middle Eocene neritic limestone in the type locality of the volcanic Barique Formation, Timor-Leste: Microfacies, age and tectonostratigraphic affinities

Abstract

Abstract Eocene shallow-water limestone is widespread in small isolated outcrops in Timor. Several occurrences of limestone in the Culocau River of Timor-Leste are significant because they lie within the type locality of the mainly volcanic Barique Formation. The tectonostratigraphic affinity of the Culocau River limestone is investigated by establishing the range of microfacies present (indicative of the inner neritic zone less than 40\u202fm deep to the outer neritic Deep Euphotic Zone), the age of the limestone using planktonic and benthic foraminifers (late Middle Eocene, probably within the 37.8–43.6\u202fMa interval), and the similarity of the limestone–volcanic association to coeval occurrences elsewhere in Timor and the region. The field association of Middle Eocene neritic limestone with volcanic-volcaniclastic rocks is widespread in Timor, but is not known along the North West Shelf of Australia. Elsewhere in Timor the association of rocks found at the Barique Formation type locality also includes Late Eocene and latest Oligocene-earliest Miocene neritic limestone. This young, mainly volcanic association (Barique Group) is usually found in coherent areas of outcrop with the Late Mesozoic Palelo Group, oceanic facies (radiolarites to carbonate pelagites), Early Jurassic Bahaman-like carbonate-bank deposits (Perdido Group) and associated units of Gondwanan origin that form some high fatus surrounded by the Barique Group, and the Lolotoi/Mutis Metamorphic Complex. This is the Overthrust Terrane Association that is distinct in outcrop area and in lithostratigraphic makeup from the pre-collision Late Carboniferous to Middle Jurassic East Gondwana Interior Rift Association and the Late Jurassic to early Late Miocene Timor-Scott Plateau Association. The Cretaceous to Early Miocene units of the Overthrust Terrane Association, including the Barique Group, are similar to coeval units in Sumba and are considered to be fragments of the fore-arc of the Banda Arc.